Dear Director,
I'd like to apply for the post of assistant which was advertised in the newspaper. I found this position quite appealing to me.
I've just graduated from high school. Luckily I'm good at English and I can speak English fluently. In addition, I have previous experience. During my stay in middle school, I used to be a volunteer and looked after the old people in a nursing home on weekends.
In short, I believe my experience and fluent oral English will be a great help for me in doing the work. I'm available for interview at any time. It would be appreciated if I can get your offer.
Sincerely,
Li Hua